In preferred manner, hydraulically-actuated pumps include at least two diaphragms. It is possible in simple manner to detect that one of the two diaphragms has broken by monitoring the pressure that exists in the space between the two diaphragms.
Hydraulically-actuated diaphragm pumps are thus known that have a composite diaphragm made up of two thin diaphragms with a thick intermediate diaphragm in the form of an elastically deformable dome. The pump has a duct formed in the thickness of the intermediate diaphragm with one end opening out to the outside of the pump and one end connected to at least one drain channel. The drain channel is also provided in the thickness of the pump diaphragm to connect the duct to the spaces that extend between each of the faces of the intermediate diaphragm and the thin diaphragm facing it. Usually, a device for detecting a breakage of a diaphragm is implemented at the outlet from the duct in the intermediate diaphragm.
Nevertheless, it is found that the thin diaphragms are not always perfectly fitted on the intermediate diaphragm. Unfortunately, the presence of air in the space between each thin diaphragm and the intermediate diaphragm greatly degrades the performance of the pump. This drawback is made even worse for a low-flowrate pump.
It is therefore appropriate to evacuate the air that is held captive in this way between the thin diaphragms and the intermediate diaphragm. Various degassing processes are known for bleeding off this air during a stage of putting the pump into operation.
An example of such a degassing process consists in a first step in using a syringe, for example to inject oil into the duct in the intermediate diaphragm. The oil then fills the drain channel and the space between the thin diaphragms and the pump diaphragm.
In a second step, the syringe is used to apply suction to the oil and thus entrain some of the air that was trapped between the thin diaphragms and the intermediate membrane.
In a third step, the detection device is mounted on the pump and the pump is set into operation with progressively increasing load so as to have the consequence of expelling the air that still remains between the thin diaphragms and the intermediate diaphragm under the effect of the suction that exists on either side of the composite diaphragm.
Nevertheless, such a degassing process is found to be lengthy and difficult to perform.
In order to mitigate that drawback, it is known to install an automatic degassing system at the outlet from the duct in the intermediate diaphragm, with this being done before installing the device for detecting breakage of a diaphragm at that location. Nevertheless, such a system is found to be extremely expensive and complex in use.